We’ve all seen it: you’re perusing the blog of your favorite skeptic firebrand when suddenly, this catches your eye on the sidebar:

…seriously? Do they really think someone reading this blog is going to want what’s being offered in this ad?

In short, it’s a simple error caused by an algorithm mistaking frequent mention of a topic as endorsement of that topic.

Some websites solicit and vet their own ads, but many use services like Google AdSense or Microsoft’s AdChoice. To figure out what’s going on with these ads, I decided to look into Google AdSense and AdWords (the advertiser side), but I assume other services work similarly (let me know in the comments if this isn’t true).

As an advertiser, you want your ads to reach people that are going to be interested in your product or service. To help with this, Google offers targeted advertising. You can target your audience in various ways. Let’s say your service is really only accessible by people in a certain region (a museum or an independent store, for example)–in that case, you might want to use location-based targeting that pays attention to internet users’ locations. Another option is targeting based on what Google calls “interest categories,” which are basically broad topical categories like health, sports, or religion. Finally, Google offers “contextual targeting,” which combines the previous elements with a keyword analysis:

Our system analyzes each site’s content and theme, considering factors such as text, language, link structure, and page structure. From these factors, Google determines the central themes of each webpage and targets AdWords ads to the page based on the advertiser’s keyword or topic selections and language and location targeting.

This isn’t the full picture, but it’s enough information for us to start to see how ads can turn up in inappropriate locations. A skeptic blog might be in Health or Alternative Medicine categories, and posts debunking some pseudoscientific health claims might feature the kind of keywords that would trigger an ad like this:

(Ryan points out that this ad, which he spotted right here on Mad Art Lab, is doubly ironic for appearing on an art blog while committing so many crimes against good design principles.)

PZ Myer writes a lot about Christianity and the ineffectiveness of prayer. Guess what I found over on Pharyngula?

Probably not what she was going for, and probably not appealing to the vast majority of her readers.

And isn’t that kind of a big point? It doesn’t actually benefit these advertisers for their ads to appear on websites where no one is interested in what they are offering.

AdWords advertisers participate in auctions to get their ads placed in desirable spots on the web. However, as far as I can tell, they don’t see the actual domains they’re bidding on unless they are targeting a specific domain. But if you’re targeting location, keywords, or interest categories, you don’t know the specific site that will feature your ad. AdWords allows advertisers to exclude specific websites or directories if they so choose, but they have to know the exact URLs; I’m betting most of these advertisers don’t realize their ads are ending up here.

So, what’s the takeaway? Me, I’m just going to keep enjoying the humorous juxtaposition of these ads and the contradictory blog content. I enjoy it so much, in fact, that I started a tumblr last week called Mistargeted Ads. If you spot an ironically misplaced ad on a blog or website you frequent, take a screen shot and send it in!

Like this:

Anne Sauer is an atheist with an appetite for science, good food, and making connections between the two. She is currently pursuing her MBA in Sustainable Management at Presidio Graduate School in San Francisco. Her favorite foods are salted caramel ice cream and chicken tikka masala. You can find her on twitter @aynsavoy.

“Here’s to the ads for psychics that pop up on skeptic blogs and the ads for Christian singles sites that pop up on atheist blogs–we’re glad your advertising dollars are being spent on us, instead of on someone who might buy what you’re selling.”